NEW YORK (AP)  An amateur athlete who died during the New York City Triathlon last summer was killed by a condition linked to high blood pressure, the medical examiner's office said Tuesday.

Esteban Neira, 32, died in the Hudson River during the swim portion of the triathlon on July 20. The cause was initially a mystery. An autopsy was inconclusive. A few of the 3,000 participants in the event speculatively blamed stinging jellyfish that had been in the river that day.

But after further testing, the medical examiner ruled the cause of the Argentine athlete's death was hypertensive cardiovascular disease.

Triathlon organizer John Korff said Neira, a father of three from Buenos Aires who worked as a consultant for Accenture, apparently was unaware he had the condition.

Hypertensive heart disease is a common killer, but its symptoms sometimes don't appear until someone is dangerously ill. It is most often associated with people who smoke, don't eat right or don't exercise.

Korff said the incident underscores that even triathletes who appear outwardly healthy should occasionally get themselves checked out by doctors.

"There are certain things you're never going to know," he said. "If you're new to the sport, make sure to get a physical."

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